This invention is concerned with processes for the production of iodopropynyl butylcarbamate (CAS NO. 55406-53-6), synonyms, 3-iodo-2-propynyl butylcarbamate; 3-iodo-2-propynyl n-butylcarbamate; 3-iodopropynyl butylcarbamate; ASC 67000; iodo-2-propynyl butylcarbamate; and iodopropynyl butylcarbamate, hereinafter collectively referred to as “IPBC.” The invention also includes the IPBC generated by these processes.
In the last several decades, IPBC has achieved widespread use as a biocide and as a fungicide. As to these usages, the use of IPBC as a fungicide has become paramount. As a fungicide, IPBC has achieved wide acceptance as a paint additive. The build up of fungus on painted surfaces is a troublesome problem particularly in southern climates. In order to prevent an unsightly appearance, particularly on outdoor painted surfaces, this fungus must be scrubbed off of the painted surface. If a small percentage of IPBC is added to the paint during it's manufacture, the development and buildup of fungus on the painted surface is eliminated.
In addition to use in paints, IPBC has achieved widespread commercial acceptance as a fungicide for treating lumber. Further, IPBC is useful as an additive for cosmetics where it functions as both a biocide and as a fungicide in order to prevent the undesirable buildup of bacteria and fungi in cosmetic formulations.
IPBC is also added to polymeric formulations in order to prevent bacterial and fungi buildups on articles which are manufactured from the polymers.
For use in paint and cosmetics, it is desirable to have the IPBC as pure as possible, as pure IPBC is a white powder. In contrast, closely related impurities such as di- and tri-iodo compounds are colored and hence tend to tint the paint and cosmetic formulations. This tinting is very undesirable.
Metal cutting fluids tend to be used for extended periods of time. It has been known for many decades that bacterial build in these cutting fluids is undesirable from an odor point of view and from a functionality point of view. The build up of bacterial and fungicidal residue in these cutting fluids tends to detrimentally affect the lubricating properties of these cutting fluids. IPBC has also found widespread acceptance as a biocide in cutting fluids.
In the manufacture of IPBC, it is desirable to produce IPBC with the lowest possible moisture content. The process of the present invention produces a wet-cake having a very low moisture content. This low moisture content results from a superior crystalline structure.
Purity is of the utmost importance in the formation of IPBC, as impurities in IPBC tend to discolor the product. These impurities are further thought to make the IPBC more light sensitive. This light sensitivity is very important, as light degrades IPBC to an off white in color and hence makes it unsuitable for use in color sensitive products such as paint and cosmetics.
Further it is desirable to have the IPBC as pure as possible as it is often necessary to obtain regulatory approval for the use of IPBC in products such as paint and cosmetics. High concentrations of impurities in the IPBC present substantial problems as these impurities have individual and distinct toxicity profiles which must be dealt with in any approval procedure. The present invention relates to processes for the production of high yields of IPBC with low concentrations of impurities.
In this regard, processes for producing iodo alkynyl carbamates are known. For example, U.S. Pat. No. 5,693,849, issued on Dec. 2, 1997 (the '849 patent), relates to a process for producing iodo alkynyl carbamates. The process is carried out in an aqueous environment which comprises an aqueous solution of a surfactant, which can be either an acidic organic phosphate partial ester or a sulfated fatty alcohol. These are ionic surfactants. A alkynyl carbamate is dispersed in the aqueous reaction medium and iodinated with iodine in the presence of sodium hypochlorite. Among other things, the process of the present invention is distinct from the process of the '849 patent in that, in the subject invention, the surfactant is preferably nonionic. Further, the surfactant used in the '849 process are of two carefully defined classes of phosphated or sulfated compounds, and lastly the carbamate is iodinated with elemental iodine. Specific surfactants are stated to be required for the reaction of the carbamate with elemental iodine.
The production and use of IPBC is also discussed in U.S. Pat. No. 3,923,870. The process for preparing IPBC disclosed in that patent requires an initial preparation of iodopropargyl alcohol. This is a dangerous compound that must be isolated by extraction in ethyl ether. The ether then must be evaporated to yield the pure alcohol product. Iodopropargyl alcohol, is not only extremely corrosive to the skin, but also decomposes, possibly violently, at a temperature of about 125° C. so it must be very carefully handled. To form the final IPBC product, the iodopropargyl alcohol is then reacted with butyl isocyanate, which also is a strong irritant. The IPBC prepared by this process is very impure, and has a distinct odor. Further, the resultant IPBC must be further processed for purification.
EPO Publication No. 0014032 also describes a method of preparing IPBC. In this disclosure, propargyl alcohol is first reacted with an isocyanate, e.g., butyl isocyanate, to form propargyl butylcarbamate. The resulting propargyl butylcarbamate is then reacted with a slight molar excess of an iodinating agent such as a mixture of pure iodine, an alkali metal hydroxide and sodium hypochlorite in an aqueous medium, typically containing a co-solvent. To promote sufficient contact between the sparingly water-soluble alkynyl carbamate and the iodinating agent, the reaction preferably is conducted in the presence of a water miscible auxiliary solvent such as an alcohol, i.e., is an aqueous methanol solution. The method of isolating the end product is by extraction from the aqueous methanol solution. This disclosure also suggests conducting the reaction in an aqueous medium by initially dispersing or emulsifying the alkynyl carbamate, with the aid of a surfactant, but does not indicate the ultimate method of product isolation, the yield, nor the purity of the product made in this manner. Surfactants disclosed as being suitable for use, include hydrolyzed or partially hydrolyzed polyvinyl acetates, phase-transfer catalysts such as cetyl trimethyl ammonium bromide, dispersing agents such as the sodium salt of a condensate of formaldehyde and naphthalene sulfonic acid and emulsifying agents such as ethoxylated nonyl phenols.
In the EP publication, the presence of the iodopropynyl butylcarbamate is ascertained merely by infrared (IR) spectra. Viewed in the light of present day requirements, both commercial and regulatory, this data does not document the completion of the reaction. The appearance of an infrared absorption band at 2200 cm.sup.-1 also does not indicate the yield or the purity of the end product.
U.S. Pat. No. 4,297,258 also describes the reaction of propynyl butylcarbamate with iodine in an aqueous medium containing a co-solvent. The product is extracted from the reaction mixture with a water immiscible organic solvent.
Consequently, it would be desirable to produce high purity IPBC compound without the limitations (i.e., water content, etc.) set forth above.